The present invention concerns a method and apparatus for controlling the manner of operation of functional devices based upon navigational input. Such a method and apparatus is particularly useful in the application of chemical products, such as fertilizer, to agricultural or farm land. More specifically, the invention contemplates a method and apparatus for prescription application of these agricultural products to the land wherein specific chemical blends are applied in accordance with the needs of various soil types and crops.
It is known in the agricultural art that a given tract of agricultural land, or a field, possesses variable characteristics that relate and contribute to crop fertility. The presence of different soil types and existing soil constituency levels contribute to this variability. Certain areas of a field will require different farming inputs, such as pesticides, nutrients and irrigation, than other areas of the same field. The practice of matching inputs with crop soil requirements has come to be known as "prescription farming". In general, the focus of prescription farming on varying the application rates of farming inputs from point to point within a field, rather than using a single, average rate over the entire field. The goal of prescription farming is to supply crops with only the inputs that they require, and no more, to provide maximum yields.
For decades, farmers have practiced prescription farming by manually applying additional inputs in specific areas of a given field where the farmer knew from experience (and often trial and error) that such additional inputs were needed. Such manual application of inputs is relatively inaccurate and unscientific.
Attempts have also been made to mechanize the process of prescription farming. To this end, there are applicator vehicles currently on the market equipped with systems to allow application of varying rates and/or combinations of inputs. Such variable applicator vehicle systems are equipped with electronic product delivery controllers which signal the system pumps and/or motors to vary the rates of application of the various inputs carried on board the vehicle. These variable rate applicator vehicles help to increase the accuracy of application. However, the problem still remains with these systems of navigating through the field. Although a farmer can determine and vary the rate of application of a particular input, the accuracy of the prescription farming process is questionable if the farmer cannot precisely determine his position in the field during the application process as the applicator vehicle is moving.
To this end, attempts have been made to increase the accuracy of the prescription farming process by generating computer-readable maps that set forth prescriptions on a field-by-field basis. This approach contemplates a computer mounted on the applicator vehicle which interfaces with electronic product delivery controllers which control the various input pumps and motors. Although these approaches have taken steps toward more accurate prescription farming, several inadequacies remain.
First, current methods of mechanizing prescription farming use dead reckoning as a navigation method to determine the position of the applicator vehicle as it moves through the field. This means that the position of the vehicle is based at all times on its relation to a fixed starting position. The vehicle's relative position in the field is a function of a predetermined (rather than actual) speed and the vehicle travel time to determine a distance as measured from the fixed starting position. One drawback of this approach is that the vehicle must be driven at a fixed speed that has been previously provided to the on-board computer. Another drawback is that the vehicle must be driven in fairly straight and parallel lines through the field, often requiring superior driving skills on the part of the vehicle operator. Moreover, with this approach, the application process must be put on stand-by when a turn is made at the end of the field, otherwise the dead reckoning system will incorrectly determine that the vehicle is farther along in the field than its true position justifies. If the vehicle operator begins at the wrong point in the field, drives in the wrong direction, fails to maintain a straight driving path, or forgets to put the system in a stand-by mode during a turn, the application process will fail in its essential purpose because inputs will be applied at improper locations on the field. With this prior art dead reckoning approach, even the slightest operator oversight or error can result in improper application of input products to the field.
Second, current mechanized prescription farming methods require data contained on the digital prescription map to be reduced to a relatively small number of variables. Four example, if a given field requires ten rate variations of six inputs, or products, one million possible application combinations result. Prior digital prescription farming techniques are not capable of storing this much information, and instead are limited to about five variations for up to six different products. This severe restraint prohibits effective prescription determination and generation, as well as effective data management within the on-board computer.
Third, current mechanized prescription farming methods require field maps to be generated in a raster format in which each pixel on the computer monitor is assigned a discrete digital value representative of the soil type at the location of the field represented by the pixel. This protocol severely limits the size of the field that can be represented or contained on a single map while still maintaining accuracy.
In short, prior computer-based mechanized prescription farming systems have required excessive operator input with little room for human error. In addition, these systems are often unwieldy in their implementation, even with digital computer technology.